Additive manufacturing (AM) is defined by ASTM as the “process of joining materials to make objects from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing methodologies, such as traditional machining. Laser based additive manufacturing is accomplished by directing a high power laser at a target, e.g., a powder, to create a melt pool. Typically, to create the desired geometry, the laser is rastered across the substrate while material is continuously added in a process referred to as Selective Laser Sintering (SLS). SLS fuses the melt pool and/or added material into a three-dimensional object. A laser may selectively fuse small particles in the form of a powdered material by scanning cross sections on the surface of a bed of powder. These cross sections may be identified from a three-dimensional model of the part. As each cross section is scanned, the bed of powder may be lowered by a one layer thickness, and a new layer of powder may be applied on top of the scanned layer. This process may be repeated until the part is completed.
As compared to other manufacturing methods, selective laser sintering can be used to manufacture parts from a relatively wide range of materials. These materials include, for example, polymers, metals, and sand. The process may include full melting, partial melting, or liquid phase sintering.
Selective laser sintering may be used to build prototypes and production parts for use, such as in an aircraft. Selective laser sintering is capable of being used to produce parts with complex geometries within various dimensions.
Aircraft parts typically have stringent and/or extreme design requirements as compared to parts with other applications. These requirements may occur from operating environments that may have high loads and temperatures. Further, these parts also may be required to be capable of withstanding impact loads from maintenance, handling, and/or other types of impact loads. For example, some parts may need to survive usage in some airframe locations that have in-service temperature ranges from around −54 degrees Celsius to around 225 degrees Celsius.
In particular, parts that exist near areas that are heated to or near engine or exhaust temperatures may need to be serviced and handled on the ground in severe winter conditions that may be present above 48 degrees north latitude or at altitude. These conditions require the material that the parts are made of to have sufficient impact resistance at the low end of the temperature range. Simultaneously, sufficient stiffness and mechanical strength must be maintained at the high end of the temperature range to prevent failure in service.
Including reinforcing fibers into AM parts can improve certain mechanical properties, however, such properties generally are constrained to the relative length, diameter, and orientation of the reinforcing fibers and therefore may fall short of parts having the full benefit of reinforcement.